1. Field of the Invention
The present invention relates to nano-scale antennas and, more specifically, to a plasmonic nano-scale antenna.
2. Description of the Related Art
An antenna converts an electrical signal into a transmission of radio waves and converts radio waves into an electrical signal. Most antennas operate at the macro scale and are used for communications between conventional radio-frequency transceivers.
Nanotechnology is providing a new set of tools to the engineering community to design and eventually manufacture novel electronic components that may be no more than a few cubic nanometers in size and that will be able to perform specific functions, such as computing, data storing, sensing and actuation. The integration of several nano-components into a single entity, just a few cubic micrometers in size, will enable the development of more advanced nano-devices. By means of communication, these nano-devices will be able to achieve complex tasks in a distributed manner. The resulting nano-networks will enable unique applications of nanotechnology in the biomedical, industrial, environmental and military fields, such as advanced health monitoring and drug delivery systems, or wireless nanosensor networks for biological and chemical attack prevention.
Currently, enabling the communication among nano-devices is still a mostly unsolved challenge. The miniaturization of a classical antenna to meet the size requirements of nano-devices would impose very high radiation frequencies. For example, a one-micrometer-long dipole antenna would resonate at approximately 150 THz. The available transmission bandwidth increases with the antenna resonant frequency, but so does the propagation loss. Due to the expectedly very limited power of nano-devices, the feasibility of nanonetworks would be compromised if this approach were followed. In addition, it is not yet clear how a miniature transceiver could be engineered to operate at these very high frequencies. Moreover, intrinsic material properties of many common metals remain unknown at the nanoscale and, thus, common assumptions in antenna theory, such as the ideal perfect electric conductor (PEC) behavior of the antenna building components, appear not to hold in this realm.
Alternatively, the use of nanomaterials to fabricate miniature antennas may help to overcome these limitations. In one example, graphene, i.e., a one-atom thick layer of carbon atoms in a honeycomb crystal lattice, has attracted the attention of the scientific community due to its unique electronic and optical properties. The conductivity of graphene has been studied both for DC and for frequencies that range from the Terahertz Band (0.1-10 THz) up to the visible spectrum. In particular, it has been shown that it drastically changes with the dimensions or the chemical potential. For example, the infrared conductivity of infinitely large two-dimensional graphene sheets at zero chemical potential has been found to be essentially independent of frequency and equal to σ0=πe2/2h (where e refers to the electron charge and h refers to the Planck constant). Also, it has been recently shown that the lateral confinement of electrons in semi-finite-size graphene nanoribbons (GNRs) enhances the material conductivity in the Terahertz Band.
In accordance to its conductivity, the propagation of surface plasmon polariton (SPP) waves on doped graphene has been recently analytically studied and experimentally proved. SPP waves are confined EM waves coupled to the surface electric charges at the interface between a metal and a dielectric material. Many metals support the propagation of SPP waves, but usually at very high frequencies (e.g., near-infrared and optical frequency bands). In addition, the propagation of SPP waves even on noble metals, which are considered the best plasmonic materials, exhibit large Ohmic losses and cannot be easily tuned. On the other hand, SPP waves on graphene have been observed at frequencies as low as in the Terahertz Band and, in addition, these can be tuned by means of material doping.
Therefore, there is a need for an antenna that facilitates communication between nano-scale devices.